Shekalim 2:3-4

Shekalim 2:3

Let’s say that a person gathered coins saying, “These are for my shekel” but he ended up collecting more than necessary. In such a case, Beis Shammai say that the surplus is a donation to the Temple but Beis Hillel say that the surplus is not consecrated (because he only intended to consecrate the value of the shekel). If he said, “I will take my shekel from these,” then everyone agrees that the surplus is not consecrated. If he gathered money saying, “These are for a sin offering,” everyone agrees that the surplus is a donation to the Temple; if he said, “I will take money for my sin offering from these,” then everyone agrees that the surplus is not consecrated

Shekalim 2:4

Rabbi Shimon asked why the rules in the previous mishna should differ for a shekel and a sin offering. He answered that the shekel has a fixed value but a sin offering does not. Rabbi Yehuda said that the shekel also has no fixed value; when the Jews first returned from exile, they would donate gold darics (worth four shekels). Later, they would donate sela coins (worth two shekels). Still later, they donated tevain (half-sela coins) and they wanted to donate dinars (a smaller denomination still). Rabbi Shimon said that even though people used different denominations at different times, everybody still gave the same amount. This is not the case with a sin offering where one person might purchase an animal worth a sela, another for two sela, another for three, etc.